This invention relates to the art of cable winding and unwinding drums and, more particularly, to an automatic latching and unlatching mechanism for controlling the rotation of a cable drum in the unwinding direction.
The present invention finds particular utility in connection with a cable drum type mechanism by which a spare tire is supported in a stored position beneath a vehicle chassis and is lowerable from the stored position to an accessible position in which the tire engages the ground beneath the vehicle and, accordingly, the invention will be described in detail herein in connection with such a spare tire handling mechanism. At the same time, however, it will be appreciated that the invention is applicable in general to cable drum mechanisms in which a cable drum is rotatable in opposite directions to facilitate the elevating and lowering of a load.
Cable drum type spare tire handling mechanisms have been provided heretofore and, generally, have included some form of a reel or drum which is rotatable in opposite directions to provide for the winding and unwinding of a cable or other flexible connector relative thereto. The drum cable has a free end adapted to be releaseably interengaged with a spare tire and, when the cable is wound onto the drum, the spare tire is elevated into a storage position beneath the vehicle. Upon rotation of the drum in the opposite direction to unwind the cable, the spare tire is lowered to ground beneath the vehicle and, generally, is then pulled from beneath the vehicle and disconnected from the cable to enable use of the spare tire.
The storage of a spare tire beneath the chassis of a vehicle is advantageous for a number of reasons including the optimizing of available storage space and improving the aesthetics of interior portions of the vehicle where spare tires are generally stored. Such storage also avoids having to physically lift the spare tire to remove it from within the vehicle or to replace it in the vehicle and, accordingly, avoids the potential soiling and/or damaging of the clothes of the person handling the tire and/or physical injury to the user.
While cable and drum mechanisms heretofore available can provide the foregoing advantages, there are disadvantages with respect to the operation of the prior mechanisms which encumber the ease with which the mechanisms can be operated by the vehicle operator or other user. In particular, the ratchet and pawl arrangements by which a cable drum is held against rotation in the unwinding direction when the spare tire is in its stored position require manual displacement of the pawl to a drum release position to permit rotation of the cable drum in the unwinding direction and thus lowering of the spare tire. The drum is of course loaded for rotation in the unwinding direction by the weight of the spare tire, whereby manual displacement of the pawl to its drum release position requires considerable force in order to overcome the force of the ratchet teeth against the pawl element. Further, because of the location of the cable drum mechanism relative to the vehicle chassis, the pawl may not be conveniently accessible, whereby the manual actuation thereof can require the person doing so to be in a physical position which is uncomfortable and/or is such as to preclude the exertion of optimum physical force to release the pawl, thus making the drum releasing operation more cumbersome.
Moreover, accessibility to the pawl often requires the user's hand or hands to be close to and/or to engage adjacent metal components of the vehicle chassis or the cable drum mechanism, whereby manipulation of the pawl can result in injury to the user. In particular in this respect, the pawl is generally located adjacent the crankshaft by which the drum is rotated in the winding direction and, upon release of the pawl, the drum and thus the crankshaft rotate at high speed as the spare tire free falls to the ground. Thus, the rotating shaft becomes a potential cause of injury should the user's hand come into contact therewith during such rotation. Such potential injury is promoted if the pawl is spring biased to its ratchet engaging position and, thus, must be held in the release position during the unwinding rotation of the drum. If the pawl is not spring biased, then it must be reset when it is desired to return the spare tire or its replacement to the stored position. While such resetting of the pawl is not as physically difficult or potentially harmful with respect to the user, it is nonetheless a further manual operation which the user is subjected to prior to rotating the drum to return the tire to its stored position. Should the user forget to reset the pawl, then the ensuing rotation of the cable drum in the winding direction to elevate the tire to its stored position is without any restraint against rotation of the cable drum in the unwinding direction should, for example, the user lose his or her grip on the crank handle or other tool by which the drum is being rotated. It will be appreciated that the latter is potentially dangerous in that the crank handle or tool, which is removable from the crankshaft, can either rotate at high speed with the shaft or be thrown off the crankshaft during high speed rotation of the latter resulting from free fall of the tire.